In recent years, as the awareness of environmental protection increases and the concept of protecting the earth arises, since thermoelectric power generation boosts carbon emission as well as causes pollution to the environment and greenhouse effect, and nuclear power generation causes safety concerns and also results in long term and serious pollution to the environment, the development of green energy technologies has received more attention. Among all the green energy technologies, solar technology neither increases carbon emission nor causes safety concerns and therefore is an environment-friendly and clean energy technology.
However, the solar technology has been found to have the problem of low energy conversion efficiency. Under such circumstances, a back-electrode solar cell was developed. Since the electrode is disposed on the rear side to reduce blocking of sunlight, the light-irradiating area of a solar cell can be increased.
Conventional back-electrode solar cell may be roughly categorized into four types according to their structures, namely an interdigitated back contact (IBC) back-electrode solar cell, an emitter wrap through (EWT) back-electrode solar cell, a metallization wrap through (MWT) back-electrode solar cell and a metallization wrap around (MWA) back-electrode solar cell. The IBC back-electrode solar cell has the problem of serial stress due to the special shape, and it is required to place an interconnected stripe protective sheet between cells. For the MWT back-electrode solar cell, the problem lies in that it is required to carry out through holes of a silicon chip and a process to insulate the walls of the thorough holes, and the reliability of such process is low. As for the EWT back-electrode solar cell, the problem is that the connection circuit requires an encapsulating material to be integrated with a back material; besides, the long-term stability is yet to be confirmed.